The present invention relates to the field of AM stereo receivers and more particularly to a receiver having an improved tuning arrangement.
A number of systems are known which provide AM stereo transmission and reception. One of these is compatible in that the envelope of the transmitted signal contains only the sum or monophonic information (L+R) and all of the stereo information is transmitted by phase modulation of the carrier. This system, including transmitter and receiver embodiments, is shown and described in a co-pending application, Ser. No. 674,703, assigned to the same assignee as is the present invention. In the above-mentioned co-pending application, all embodiments of the stereo receiver for demodulating the compatible signal do so in a symmetrical fashion; i.e., providing signals in quadrature which are then demodulated in synchronous detectors to provide sum and difference signals and, ultimately, L and R. While all embodiments shown in said co-pending application are practical embodiments, a receiver utilizing synchronous detectors in both sum and difference channels may be difficult to tune properly, as the beats during the tuning-in period would have to be blocked out of the audio channels, and other provisions made for tuning.